Download Ham Radio Glossary Alternating current (AC) -

Ham Radio Glossary
Alternating current (AC) -- Electrical current that flows first in one direction in a wire and then in the other.
The applied voltage is also changing polarity. This direction reversal
continues at a rate that depends on the frequency of the ac.
Amateur operator -- A person holding a written authorization to be the
control operator of an amateur station.
Ampere (A) -- The basic unit of electrical current.
Amplitude modulation (AM) -- A method of combining an information
signal and an RF (radio-frequency) carrier. In double-sideband voice AM
transmission, we use the voice information to vary (modulate) the
amplitude of an RF carrier. Shortwave broadcast stations use this type of AM, as do stations in the Standard
Broadcast Band (535-1710 kHz). Few amateurs use double-sideband voice AM, but a variation, known as
single sideband, is very popular.
Antenna tuner -- A device that matches the antenna system input impedance to the transmitter, receiver or
transceiver output impedance. Also called an antenna-matching network, impedance-matching network or
Transmatch.
Audio Frequency Oscillator -- produces frequencies in the audio range, about 16 Hz to 20 kHz.[2]
Autopatch -- A device that allows repeater users to make telephone calls through a repeater.
Balun -- A device used to couple a balanced antenna to an unbalanced
feed line (e.g., dipole to coax). A balun is a type of transformer. Baluns
convert between impedances and symmetry of feedlines and antennas.
To avoid feed line radiation, baluns are typically used as a form of
choke attached at the antenna feed point to prevent the coaxial cable
from acting as an antenna and radiating power. This typically is needed
when a balanced antenna (for instance, a dipole) is fed with coax;
without a balun, the shield of the coax could couple with one side of the dipole, becoming part of the
antenna and unintentionally radiating.
Balanced Modulator -- A device that modifies a signal, usually in the form of an amplitude modulated (AM)
radio signal. It takes the original signal that has both sidebands and a carrier signal, and then modulates it so
that only the sideband signals come through the output. This creates a balanced signal, as there is less noise
because the carrier signal has been removed.
Band-pass filter -- A circuit that passes a range of frequencies and attenuates or rejects signals above and
below the desired band (passes the desired band).
Bandwidth -- Bandwidth describes the range of frequencies that a radio transmission occupies.
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Beacon station -- An amateur station transmitting communications for the purposes of observation of
propagation and reception or other related experimental activities.
Beat-frequency oscillator (BFO) -- A receiver circuit that provides a signal to the
detector. The BFO signal mixes with the incoming signal to produce an audio tone
for CW reception. A BFO is needed to copy CW and SSB signals.
Beam antenna -- A directional antenna. A beam antenna must be rotated to
provide coverage in different directions. A Yagi is an example of a beam antenna.
See Yagi.
Block diagram -- A drawing using boxes to represent sections of a complicated device or process. The block
diagram shows the connections between sections.
Broadcasting -- Transmissions intended to be received by the general public, either direct or relayed.
Capacitance -- A measure of the ability of a capacitor to store energy in an electric field. The SI unit of
capacitance is the Farad (F) (Michael Faraday). The greater the area of the plates and the smaller the
distance between the plates, the greater the capacitance (the greater amount of charge can be stored in the
capacitor. The type of dielectric material (an insulator) between the plates also affects the capacitance.
Capacitor -- An electrical component usually formed by separating two conductive plates with an insulating
material. A capacitor stores energy in an electric field.
Capacitive reactance -- Capacitive reactance is an opposition to alternating current across a capacitor.
Capacitive reactance XC is inversely proportional to the signal frequency f and the capacitance, C.
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𝑋𝐶 = 2𝜋𝑓𝐶
Coaxial cable -- Coax. A type of unbalanced feed line with one conductor inside the
other.
Colour code -- A system in which numerical values are assigned to various colours.
Coloured stripes are painted on the body of resistors and sometimes other components to show their value.
(black, brown, R,O,Y,G,B,V,grey, white; respectively 0,1,2,3,4,5,6,7,8,9
Continuous wave (CW)--Morse code telegraphy.
CQ -- "Calling any station": the general call when requesting a conversation with anyone.
Crystal oscillator -- A device that uses a quartz crystal to keep the frequency of a transmitter constant.
Crystal-controlled transmitter -- A simple type of transmitter that consists of a
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crystal oscillator followed by driver and power amplifier stages.
CTCSS -- Continuous tone coded squelch system. A sub-audible tone system used on some repeaters. When
added to a carrier, a CTCSS tone allows a receiver to accept a signal. Also called PL tone.
Cubical quad antenna -- An antenna built with its elements in the shape
of four-sided loops.
D region -- The lowest region of the ionosphere. The D region contributes
very little to short-wave radio propagation. It acts mainly to absorb
energy from radio waves as they pass through it. This absorption has a
significant effect on signals below about 7.5 MHz during daylight.
Delta loop antenna -- A variation of the cubical quad antenna with triangular elements.
Detector -- The stage in a receiver in which the modulation (voice or other information) is recovered from
the RF signal
Digipeater -- A packet-radio station used to retransmit signals that are specifically addressed to be
retransmitted by that station.
Digital communications -- Computer-based communications modes. This can include data modes like packet
radio and text-only modes like radioteletype (RTTY).
Dipole antenna -- A dipole antenna is a radio antenna the most basic and popular antenna type. It comes in
various geometries (i.e. "rabbit ears" television antenna), with
different feeding mechanisms and radiating elements (as the driven
element in more complex antennas, such as the Yagi). This antenna
is the simplest practical antenna from a theoretical point of view.
Dipole antennas were invented by German physicist Heinrich Hertz
around 1886 in his pioneering experiments with radio waves. As of
today the dipole antenna is probably the most common antenna
type (See Half-wave dipole. A dipole need not be ½ wavelength
long.)
Direct current (DC) -- Electrical current that flows in one direction
only.
Director -- An element in front of the driven element in a Yagi and some other directional antennas.
Driven element -- The part of an antenna that connects directly to the feed line.
Dummy load -- A station accessory that allows you to test or adjust transmitting equipment without sending
a signal out over the air. Also called dummy antenna.
Duplexer -- A device that allows a dual-band radio to use a single dual-band antenna.
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DX – Distance or foreign countries.
E region -- The second lowest ionospheric region, the E region exists only during the day. Under certain
conditions, it may refract radio waves enough to return them to Earth.
Earth ground -- A circuit connection to a ground rod driven into the Earth or to a cold-water pipe made of
copper that goes into the ground.
Electric field -- An electric field exists in a region of space if an electrically charged object placed in the region
is subjected to an electrical force. Electric field is often given in volts per metre (V/m).
Electromotive force (EMF) – A voltage or the force or pressure that pushes a current through a circuit.
Emergency -- A situation where there is a danger to lives or property.
Emission -- The transmitted signal from an amateur station.
Emission types -- Term for the different modes authorized for use on the Amateur Radio bands. Examples
are CW, SSB, RTTY and FM.
F region -- A combination of the two highest ionospheric regions, the F1 and F2 regions. The F region refracts
radio waves and returns them to Earth. Its height varies greatly depending on the time of day, season of the
year and amount of sunspot activity.
Feed line -- The wires or cable used to connect a transmitter, receiver or transceiver to an antenna. See
Transmission line.
Filter -- A circuit that will allow some signals to pass through it but will greatly reduce the strength of others.
Frequency -- The number of complete cycles of an alternating current that occur per second. The unit of
frequency is the hertz (Hz).
Frequency Multiplier -- an electronic circuit that generates an output signal whose output frequency is a
harmonic (multiple) of its input frequency.
Frequency bands -- A group of frequencies where amateur communications are authorized.
Frequency coordination -- Allocating repeater input and output frequencies to minimize interference
between repeaters and to other users of the band.
Frequency discriminator -- A type of detector used in some FM
receivers.
Frequency modulated (FM) or phone -- The type of signals used to
communicate by voice (phone) over most repeaters. FM is a method
of combining an RF carrier with an information signal, such as voice.
The voice information (or data) changes the RF carrier frequency in the
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modulation process. (see Amplitude modulation). As you might suspect, we use voice or data to vary the
frequency of the transmitted signal. FM broadcast stations and most professional communications (police,
fire, taxi) use FM. VHF/UHF FM voice is the most popular amateur mode.
Fuse -- A thin metal strip mounted in a holder. When too much current passes through the fuse, the metal
strip melts and opens the circuit.
Gain -- An increase in the effective power radiated by an antenna in a certain desired direction, or an
increase in received signal strength from a certain direction. This is at the expense of power radiated in, or
signal strength received from, other directions.
Giga -- The metric prefix for 109, or a billion times 1,000,000,000) e.g. GHz (gigahertz)
Ground-wave propagation -- The method by which radio waves travel along the Earth's surface.
Half-wave dipole -- A basic antenna used by radio amateurs. It consists of a length of wire or tubing, opened
and fed at the center. The entire antenna is ½ wavelength long at the desired operating frequency.
Harmonics -- Signals from a transmitter or oscillator occurring on whole-number multiples (2×, 3×, 4×, etc) of
the desired operating frequency (e.g. 12 Hz, 24 Hz, 36 Hz, 48 Hz…).
High-pass filter -- A filter designed to pass high-frequency signals, while blocking lower-frequency signals.
Impedance -- The opposition to electric current in a circuit. Impedance includes factors other than
resistance, and applies to alternating currents. Ideally, the characteristic impedance of a feed line is the
same as the transmitter output impedance and the antenna input impedance.
Impedance-matching device -- A device that matches one impedance level to another. For example, it may
match the impedance of an antenna system to the impedance of a transmitter or receiver. Amateurs also call
such devices a Transmatch, impedance-matching network or antenna tuner.
Inductance -- A measure of the ability of a coil to store energy in a magnetic field. The symbol L is used for
inductance, in honour of the physicist Heinrich Lenz. In the SI system the unit of inductance is the henry (H),
named in honor of Joseph Henry.
Inductor -- An electrical component usually composed of a coil of wire wound on a central core (solenoid).
An inductor stores energy in a magnetic field.
Inductive reactance -- is an opposition to the change of current on an inductive element (Lenz’s Law).
Inductive reactance XL is proportional to the sinusoidal signal frequency f and the inductance L. The loops of
a solenoid will tend to induce currents in neighboring coils in opposition to the magnetic flux change. The
counter-emf is the source of the opposition to current flow XL = 2fL . The SI unit of reactance is the ohm.
(See Capacitive reactance.)
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Input frequency -- A repeater's receiving frequency. To use a repeater, transmit on the input frequency and
receive on the output frequency.
Insulator -- A material that maintains a tight grip on its electrons, so that an electric current cannot pass
through it (within voltage limits).
Intermediate frequency (IF) -- The output frequency of a mixing stage in a superheterodyne receiver. The
subsequent stages in the receiver are tuned for maximum efficiency at the IF.
Ionizing radiation -- Electromagnetic radiation that has sufficient energy to knock electrons free from their
atoms, producing positive and negative ions. X-rays, gamma rays and ultraviolet radiation are examples of
ionizing radiation
Ionosphere -- A region of electrically charged (ionized) gases high in the atmosphere. The ionosphere bends
radio waves as they travel through it, returning them to Earth. Also see sky-wave propagation.
Limiter -- A stage of an FM receiver that makes the receiver less sensitive to amplitude variations and pulse
noise.
Linear Amplifier -- An electronic circuit whose output is proportional to its input, but capable of delivering
more power into a load. The term usually refers to a type of radio-frequency (RF) power amplifier, some of
which have output power measured in kilowatts, and are used in amateur radio.
Line-of-sight propagation -- The term used to describe VHF and UHF propagation in a straight line directly
from one station to another.
Lower sideband (LSB)--The common single-sideband operating mode on the 40, 80 and 160-meter amateur
bands.
Low-pass filter -- A filter that allows signals below the cutoff frequency to pass through and attenuates
signals above the cutoff frequency.
Maximum useable frequency (MUF) --- The highest-frequency radio signal that will reach a particular
destination using sky-wave propagation, or skip. The MUF may vary for radio signals sent to different
destinations.
MAYDAY -- From the French m'aidez (help me), MAYDAY is used when calling for emergency assistance in
voice modes.
Mega -- The metric prefix for 106, one million times or times 1,000,000.
Mixer -- or frequency mixer, is an electrical circuit that creates new frequencies from two signals applied to
it. In its most common application, two signals at frequencies f1 and f2 are applied to a mixer, and it produces
new signals at the sum f1 + f2 and difference f1 − f2 of the original frequencies, called heterodynes. Other
frequency components may also be produced in a practical frequency mixer. A key component of a
superheterodyne receiver is a mixer used to move received signals to a common intermediate frequency.
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Mobile device -- A radio transmitting device designed to be mounted in a vehicle. A push-to-talk (PTT) switch
activates the transmitter.
Modem -- Short for modulator/demodulator. A modem modulates a radio signal to transmit data and
demodulates a received signal to recover transmitted data.
Modulate -- To vary the amplitude, frequency, or phase of a radio-frequency signal.
Modulation -- Radio transmission involves putting audio frequency information on a much higher frequency
electromagnetic wave called a carrier wave. The process of superimposing the "electrical image" of the
sound information on the carrier wave is called modulation, and there are two commonly used schemes:
amplitude modulation (AM) and frequency modulation
(FM). Either form of modulation produces frequencies
which are the sum and the difference of the carrier and
modulation frequencies - these frequencies are called
sidebands.
Offset-- For a repeater, offset refers to the difference between its transmitting and receiving frequencies.
Also the 300 to 1000-Hz difference in CW transmitting and receiving frequencies in a transceiver.
Ohm -- The basic unit of electrical resistance, used to describe the amount of opposition to current
= 1000 ohms).
(1 k
Ohm's Law -- A basic law of electronics. Ohm's Law gives a relationship between voltage (E), current (I) and
resistance (R). The voltage applied to a circuit is equal to the current through the circuit times the resistance
of the circuit (E = IR). (or I = E/R, and R = E/I)
Open circuit -- An electrical circuit that does not have a complete path, so current can't flow through the
circuit (off).
Open repeater -- A repeater that can be used by all hams who have a license that authorizes operation on
the repeater frequencies.
Packet radio -- A system of digital communication whereby information is broken into short bursts. The
bursts ("packets") also contain addressing and error-detection information.
Parasitic element -- Part of a directive antenna that derives energy from mutual coupling with the driven
element. Parasitic elements (reflector and director elements) are not
connected directly to the feed line.
Peak envelope power (PEP) -- The average power of a signal at its largest
amplitude peak.
Phone -- Another name for voice communications.
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Phonetic alphabet -- Standard words used on voice modes to make it easier to understand letters of the
alphabet, such as those in call signs. The call sign VE4NIR stated phonetically is Victor Echo Four November
India Romeo (Nishadh).
PNP transistor -- A transistor that has a layer of N-type semiconductor material sandwiched between layers
of P-type semiconductor material.
Polarization -- The electrical-field characteristic of a radio wave. An antenna that is parallel to the surface of
the earth, such as a dipole, produces horizontally polarized waves. One that is perpendicular to the earth's
surface, such as a quarter-wave vertical, produces vertically polarized waves. An antenna that has both
horizontal and vertical polarization is said to be circularly polarized.
Portable device -- A radio transmitting device designed to have a transmitting antenna that is generally
within 20 centimeters of a human body.
Power -- The rate of energy consumption. We calculate power in an electrical circuit by multiplying the
voltage applied to the circuit times the current through the circuit (P = IE). (or P=IV, P=I2R, P = V2/R)
Power supply -- A circuit that provides a direct-current output at some desired voltage from an ac input
voltage.
Product detector -- A device that allows a receiver to process CW and SSB signals.
Propagation -- The study of how radio waves travel.
Q signals or Q codes -- Three-letter symbols beginning with Q. Used on CW to save time and to improve
communication. Some examples are QRS (send slower), QTH (location), QSO (ham conversation) and QSL
(acknowledgment of receipt).
QRL? -- Ham radio Q signal meaning "Is this frequency in use?"
QSL card -- A postcard that serves as a confirmation of communication between two hams.
QSO -- A conversation between two radio amateurs (eyeball QSO – a face-to-face conversation).
Quarter-wavelength vertical antenna -- An antenna constructed of a quarter-wavelength long radiating
element placed perpendicular to the earth.
Radio Frequency Oscillator -- produces signals in the radio frequency (RF) range
about 100 kHz to 100 GHz.
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Radio-frequency interference (RFI) -- Disturbance to electronic equipment
caused by radio-frequency signals.
Radioteletype (RTTY) -- Radio signals sent from one teleprinter machine to
another machine. Anything that one operator types on his teleprinter will be printed on the other machine.
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Also known as narrow-band direct-printing telegraphy.
Reactance -- In electrical and electronic systems, reactance is the opposition of a circuit element to a change
of electric current or voltage, due to that element's inductance or capacitance. A built-up electric field
resists the change of voltage on the element, while a magnetic field resists the change of current. The notion
of reactance is similar to electrical resistance, but they differ in several respects.
Capacitance and inductance are inherent properties of an element, just like resistance. Reactive effects are
not exhibited under constant direct current, but only when the conditions in the circuit change (A.C. circuit).
Thus, the reactance differs with the rate of change, and is a constant only for circuits under alternating
current of constant frequency. Both share the same SI unit, the ohm.
Receiver--A device that converts radio waves into signals we can hear or see.
Reflection -- Signals that travel by line-of-sight propagation are reflected by large objects like buildings.
Reflector – The passive or parasitic element behind the driven element in a Yagi and some other directional
antennas.
Repeater station -- An amateur station that automatically retransmits the signals of other stations.
Resistance -- The ability to oppose an electric current. SI unit is the ohm ()
Resistor -- Any material that opposes a current in an electrical circuit. An electronic component specifically
designed to oppose or control current through a circuit.
Resonant Circuit -- A condition of resonance will be experienced in a tank circuit when the reactances of the
capacitor and inductor are equal to each other XL = XC. Because inductive reactance increases with increasing
frequency and capacitive reactance decreases with increasing frequency, there will only be one frequency
where these two reactances will be equal.
Resonant frequency -- The desired operating frequency of a tuned circuit. In an antenna, the resonant
frequency is one where the feed-point impedance contains only resistance.
RF burn -- A burn produced by coming in contact with exposed RF voltages.
RF carrier -- A steady radio frequency signal that is modulated to add an information signal to be
transmitted. For example, a voice signal is added to the RF carrier to produce a phone emission signal.
RF radiation -- Waves of electric and magnetic energy. Such electromagnetic radiation with frequencies as
low as 3 kHz and as high as 300 GHz are considered to be part of the RF region.
RF safety -- Preventing injury or illness to humans from the effects of radio-frequency energy.
Rig--The radio amateur's term for a transmitter, receiver or transceiver.
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RST -- A system of numbers used for signal reports: R is readability, S is strength and T is tone. (On singlesideband phone, only R and S reports are used.)
Selectivity--The ability of a receiver to separate two closely spaced signals.
Sensitivity--The ability of a receiver to detect weak signals.
Shack--The room where an Amateur Radio operator keeps his or her station equipment.
Sidebands -- The sum or difference frequencies generated when an RF carrier is mixed with an audio signal.
Single-sideband phone (SSB) signals have an upper sideband (USB -- that part of the signal above the carrier)
and a lower sideband (LSB -- the part of the signal below the carrier). SSB transceivers allow operation on
either USB or LSB.
Silent Key -- SK. Euphemism for a deceased amateur radio operator.
Simplex operation -- Receiving and transmitting on the same frequency. See duplex operation.
Single Sideband (SSB) phone -- A common mode of voice operation on the amateur bands. SSB is a form of
amplitude modulation. The amplitude of the transmitted signal varies with the voice signal variations.
Skip zone -- An area of poor radio communication, too distant for ground waves and too close for sky waves.
Sky-wave propagation -- The method by which radio waves travel through the ionosphere and back to Earth.
Sometimes called skip, sky-wave propagation has a far greater range than line-of-sight and ground-wave
propagation.
SOS -- A Morse code call for emergency assistance.
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Specific absorption rate (SAR) -- A term that describes the rate at which RF energy is absorbed into the
human body. Maximum permissible exposure (MPE) limits are based on whole-body SAR values.
Splatter -- A type of interference to stations on nearby frequencies. Splatter occurs when a transmitter is
overmodulated.
Spurious emissions -- Signals from a transmitter on frequencies other than the operating frequency.
Standing-wave ratio (SWR) -- Sometimes called voltage standing-wave ratio (VSWR). A measure of the
impedance match between the feed line and the antenna. Also, with a Transmatch in use, a measure of the
match between the feed line from the transmitter and the antenna system. The system includes the
Transmatch and the line to the antenna. VSWR is the ratio of maximum voltage to minimum voltage along
the feed line. Also the ratio of antenna impedance to feed-line impedance when the antenna is a purely
resistive load.
Sunspot cycle -- The number of sunspots increases and decreases in a predictable cycle that lasts about 11
years.
SWR meter -- A measuring instrument that can indicate when an antenna system is working well. A device
used to measure SWR. An SWR Bridge does the same thing.
Third-party communications -- Messages passed from one amateur to another on behalf of a third person.
Transceiver -- A radio transmitter and receiver combined in one unit.
Transistor -- A solid-state device made of three layers of semiconductor material. See NPN transistor and
PNP transistor.
Transmission line -- The wires or cable used to connect a transmitter or receiver to an antenna. Also called
feed line.
Troposphere -- The region in Earth's atmosphere just above the Earth's surface and below the ionosphere.
Tropospheric bending -- When radio waves are bent in the troposphere, they return to Earth farther away
than the visible horizon.
Tropospheric ducting -- A type of VHF propagation that can occur when warm air overruns cold air (a
temperature inversion).
Twin-lead cable is a balanced two-conductor flat cable used as a transmission line to carry radio frequency
(RF) signals. It is constructed of two multistranded copper or copperclad steel wires, held a precise distance
apart by a plastic (usually polyethylene) ribbon.
Ladder Line Fed Dipole Antenna
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300 ohm Twin-lead
Ladder line or "window line" is a variation of twin lead which is constructed similarly except that the
polyethylene webbing between the wires which holds them apart has "windows" cut in it.
Unbalanced line -- Feed line with one conductor at ground potential, such as coaxial cable.
Upper sideband (USB)--The common single-sideband operating mode on the 20, 17, 15, 12 and 10-meter HF
amateur bands, and all the VHF and UHF bands.
Variable-frequency oscillator (VFO) -- An oscillator used in receivers and transmitters. The frequency is set
by a tuned circuit using capacitors and inductors. The frequency can be changed by adjusting the
components in the tuned circuit.
Volt (V) -- The basic unit of electrical pressure or EMF.
Watt (W) -- The unit of power in the metric system. Power is the rate at witch work is done or energy
transformed (usually electrical energy is dissipated as heat energy).The watt describes how fast a circuit
“uses” electrical energy.
Wavelength -- Often abbreviated λ. The distance a radio wave travels in one RF cycle. The wavelength
relates to frequency. Higher frequencies have shorter wavelengths.
X -- In electrical equations, this letter stands for "Reactance."
Yagi antenna -- The most popular type of amateur directional (beam) antenna. It has one driven element
and one or more additional elements.
Z -- In electrical equations, this is used to mean "Impedance."
https://www.youtube.com/watch?v=kifC0HsYRy4
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